I hope you are not really using the Schwartzian transform in Rakudo as it is one of the worst ways to optimize a sort-by-generated-key operation!

Actually it's an implementation detail about which I don't care really much. Correctness first, performance later. I just called it a Schwartzian Transform because that's the name that most perl programmers use for the sort-by-generated-key operation.

Looking at the source it seems to do something close to what you proposed.